Steel belts for tires are made of a plurality (about 30) of round steel wires formed into plies which provide strength with flexibility to automotive tires. In their manufacture, the wires are provided in the form of large rolls which must be unwound and fed to the braiding machinery in a manner that does not reduce the strength of the wire or affect its straightness. The current practice is to apply a tension of about 10 lbs. to the wire and pass the wire through at least one assembly of rollers to guide the wires in parallel along the required path. The linear speed Of the wires is about 3 feet per second (0.9 m/s).
The rollers currently used are illustrated in FIG. 1. These rollers have a central shaft 1 passing through opening 2 in steel assembly frame 3. Nut 4 acts against flange 5 and washer 6 to hold the roller in frame 3 as a complete guide assembly. The rolling member of the roller is made of alumina tube 7 that rotates with the aid of two mechanical bearings 8. Bearings 8 are made of outer ring 9, outer-ring ball race 10, inner-ring ball race 11, inner ring 12, and ball bearing 13. Lubricant is typically used to lubricate the movement of ball bearing 13 in races 10 and 11.
Outer ring 9 and races 10, 11 are spaced apart from frame 3 by a distance, d, which is open to the atmosphere outside the roller. Through this space enters a significant quantity of air-borne dust and, importantly, scale and rust flakes from the surface of the wire being transported over the surface of the roller. After only about 2 months of use, the amount of accumulated dust, scale, and rust is sufficient to cause the bearings to seize. The roller stops rotating although the forces acting on the wire cause the wire to drag across the surface of alumina tube 7. From the friction, a groove is cut in the surface of the guide and the wire is flattened from the abrasion. Such damage to the wire reduces the wire strength and makes it more susceptible to kinks and bending.
The conventional rollers are removed from the roller frame with great difficulty due to the structure of the roller. A seized beating 8 tightly holds the bearing to central shaft 1 so removal of nut 4 does not permit central shaft 1 to be extricated from frame 3. The roller must be cut in half through alumina tube 7 and central shaft 1. A hammer is used to sharer tube 7, and a cutting torch is used on central shaft 1. Removal of a single roller in an assembly takes at least 30 minutes by an experienced technician. In fact, the replacement process is of sufficient difficulty that most commercial facilities wait until several rollers require replacement before any are replaced. Wire quality suffers in the meantime.
It would be desirable to have a roller guide that was able to resist seizing due to accumulations of airborne dust as well as scale and rust coming from metal wire being guided by the rollers.
It would also be beneficial to have a roller guide structure that would permit rapid replacement of nonfunctional rollers without destruction of the roller elements.